This research concerns itself with how subjects learn a form of compensatory speech when confronted with an alteration in oral contours. The oral contour change is created by supplying subjects with experimental dental prostheses of various forms. A multi-faceted approach is taken, combining acoustical analysis of speech, subjective reactions of subjects, and physiological measurements (tongue, jaw and larynx activity; aerodynamics). New directions are to study subjects who have had articulation defects as children, but who now display normal speech; to evaluate real-time ultrasonic scanning as a means of studying tongue activity during speech, and to use this methodology to verify predictions of acoustical models of tongue configuration; to describe left-right asymmetries in articulation, including the speech consequences of progressive changes in symmetry of prosthodontic appliances.